This invention relates generally to large telescopes or stellar interferometers, and, more particularly, to a novel optical fiber stellar interferometer having high resolving power and greatly increased sensitivity.
There are many occassions when it becomes necessary to study objects located at great distances from an observer or observation station. For example, one such occassion arises with the study and investigation of the stellar system, that is the stars, planets and other satellites. In particular, even with the large telescopes in use today accurate size and shape determinations of stars are virtually impossible. In order to increase the capability of today's large telescopes, some of these telescopes have been modified to produce what is more commonly referred to as stellar interferometers.
In the conventional stellar interferometer, light is deflected from two separate points by means of plain mirrors and directed into the telescope so as to interfere, forming fringes. The fringes formed are similar to fringes formed by two slits. A point source leads to a system of fringes whose intensity difference reaches a maximum midway between the slits and falls off in either direction. A pair of sources leads to a superposition of two such patterns. The separation of the two fringe patterns depends upon the angular separation of the sources. The fringe period depends upon the distance between the slits. By varying this distance, the patterns may be made to intermesh to vary the fringe visibility (normalized difference between maximum and minimum intensities). Measurement of the variation of fringe visibility as a function of the plain mirror separation permits the accurate determination of the angular separation of the subject stars. The effective resolution of the telescope (1.22 .lambda./D) is increased since the factor D becomes the separation of the mirrors rather than the diameter of the telescope objective. The fringes are produced by the change in relative phase with position in the plane of the fringes.
With stellar interferometers in use today a problem generally results as a result of the low light level associated with these fringes. In addition, there is the problem of stellar interferometer instability due to the long path lengths and associated lack of mechanical rigidity. It would therefore be highly desirable to provide a stellar interferometer with the capability of providing information sufficient to make accurate size and shape determinations of, for example, stars.